Hundreds of homes in Todmorden, Walsden and Hebden Bridge were under water after torrential rain, hail and lightning lashed the district.
Lightning strikes on electricity sub-stations blacked out large areas, roads were washed out and boulders dumped on town centre streets.
More than 350 emergency calls were made to the fire brigade between 6pm and 11.30pm.
In Todmorden, up to eight feet of water poured into houses in Eagle Street and a short circuit sparked a house fire in Owlers Walk.
The River Calder rose more than five feet in just 20 minutes – and later swelled to more than seven feet. Flood sirens were sounded at 8pm.
St Joseph's Primary School, Todmorden, was shut today after water poured in.
Drivers had to be rescued from floating cars on the Halifax Road between Hebden Bridge and Todmorden and businesses were destroyed in Market Street, Hebden Bridge.
Watch manager David Rawlinson, of Todmorden fire station, said: "We were called from one flood to another. It was coming down quicker than we could pump.
"Drains couldn't cope and I saw people bailing out their homes. I have never seen that severity of weather."
Dozens of fire alarms were triggered by the storm, stretching emergency services even further. Fire crews from Halifax, Mytholmroyd, Todmorden, Haworth, Bacup and a specialist team from Cookridge in Leeds turned out.
Police closed several roads, including Rochdale Road and Victoria Road in Todmorden. Railway embankments collapsed in three places between Todmorden and Rochdale, disrupting train services today.
And it took engineers until 5.30 am to reconnected the electricity supply to large areas around Hebden Bridge and Todmorden.
In Walsden, Transco investigated a suspected gas leak in Winterbutlee Road.
Calderdale Council worked through the night to clear roads, repair damage and hand out sandbags. Engineers were assessing damage to roads today.